1. Field of the Invention
This invention relates to an improved drug dispensing intrauterine device. In a preferred embodiment this invention concerns an improved intrauterine device for dispensing locally to the uterus an interceptive agent for terminating pregnancy.
2. The Prior Art
Presently, a critical need exists for an acceptable means for the direct continuous delivery of drugs directly (locally) to the uterus. In the prior art, it is most common to administer drugs to the uterus systemically, such as by injection, by ingestion or by intravenous infusion. With systemic administration, the amount of drugs needed to achieve the desired uterine purpose is so large that serious undesirable side effects often occur in many body organs.
Vaginal suppositories are another prior art drug form which has been used to administer drugs to the uterus, since some of the vaginally-administered drug which is absorbed through the vaginal walls passes via the circulatory system to the uterus. This method of delivery is essentially systemic and thus leads to the same serious side effects.
In my earlier patent applications U.S. Ser. No. 185,208 now U.S. Pat. No. 3,896,819, filed Sept. 30, 1971, and U.S. Ser. No. 281,445 filed Aug. 17, 1972, now U.S. Pat. No. 3,845,761, I disclose intrauterine devices which contain drugs and which administer a controlled flow of these drugs locally to the uterus. Such devices deliver drugs locally to the uterus only for a finite period of time and then must be removed either because the need for medication has passed or because the supply of drug in the device is exhausted and a new device is required. With conventional devices this removal is a major problem. The uterus is lined with an extremely delicate vessel-rich and gland-rich tissue, the endometrium, which surrounds and intimately contacts any object placed within it. Any probing for or the twisting and manipulating of an intrauterine device to effect its removal will almost certainly gouge and disrupt (or very likely damage) the endometrium and the vessels and glands it contains. Also, the geometry of the uterine cavity and cervix poses further complications as the cervix, through which any device must be removed, is relatively inaccessible and substantially smaller in diameter than the uterus. For these reasons, the removal of intrauterine devices is now almost always carried out by skilled medical personnel.
Attempts to make intrauterine devices in a shape or size which is easier to remove often introduces further complications since easy removal is, almost by definition, antagonistic to an acceptable degree of uterine retention. A high degree of uterine retention is critical to the success of a drug dispensing intrauterine device. Premature expulsion of the device by the uterus is highly undesirable as it results in the premature termination of drug administration. To give the desired therapy, the device must be retained in the uterus for the entire period planned. A device which is easily inserted and removed is also easily expelled. Conversely, a device having good retention characteristics is difficult to insert or remove without damage.
Insertion has been facilitated in the prior art by forming a uterine-retentive shaped device from metal or plastic having an elastic memory, deforming the device by placing it in a narrow straight flexible insertion tube, guiding one end of the tube to and through the cervix, and extruding the device out of the insertion tube into the uterus where, as a result of its elastic memory, it assumes its uterine retentive shape. While this method promotes an otherwise difficult insertion, it is not effective to effect removal, as the manipulation needed to introduce an intrauterine device into an "insertion" tube for removal is at least as harmful to the uterine tissues as the removal itself would be.